Car retarder control system



Dec. 3, 1957 R. F. ALBRIGHTON CAR RETARDER CONTRQL SYSTEM INVEN'TOR BREALBRlGHToN .Sol

Dec. 3, 1957 R. F. ALBRIGHTON CAR RETARDER CoNTRoL SYSTEM 4 Sheets-Sheet 2 Filed June 6. 1955 Dec. 3, 1957 Filed June 6. 1.955

R. F. ALBRIGHTON CAR RETARDER vCONTROL SYSTEM 4 sheets-sheet s FIG. 2A.

u RI-:TARDERS "N s ,FIC.2B.O

2TN v CAR RETARDERS l2TI s TP MODIFICATION FIG 3B* Is PERMITTED ICK MODIFICATIoN IN FIG' 3C' ACCORDANCE wITI-I PERFORMANCE OF CAR CAR ETARDERS HIS ATTORNEY Dec. 3, 1957 R. F. ALBRIGHTON 2,814,996

CAR RETARDER CONTROL SYSTEM A;

Filed June v6. 1955 Y 4 shams-sheet 4 FIG. 2F.

Y gRETARDERS CK SHUNT RENDERs MCDIHCATION.; |N ACCORDANCE WITH PERFORMANCE FIG. 3G.r oF CAR INEFFECTWE 2VTN IXP ICK meg-5g.

IN V EN TOR.-

' REALBRIGHTCN ymw HlS ATTORNEY United States Patent O CAR RETARDER CONTROL SYSTEM Reginald F. Albrighton, Rochester, N. Y., assigner to General Railway Signal Company, Rochester, N. Y.

Application .inne 6, 1955, Serial No. 513,321

7 Claims. (Cl. 104-26) This invention relates to car retarder control systems for railroads, and it more particularly pertains to automatic release control for car retarders of the track brake type.

In a car retarder control system such as is disclosed .in the U. S. patent application of Kendall et al., Serial No. 513,364 led of even date with the present application, certain car retarders known as group car retarders `are automatically operated to release cars at speeds se- .lected in accordance with the performance of such cars Vin approaching the associated car retarders. If it is a relatively long cut of cars, however, that is being retarded, .it is desirable to release the cut at a speed somewhat lower than the speed that would normally be selected by the automatic releasing means that is normally eifective.

The present invention makes use of the detector track section for the track switch immediately preceding each of the group car retarders as a part of a detecting system to detect the presence of long cuts of cars as distinctive from short cuts. If successive cars are separated by a distance greater than the length of the detector track section, these cars are not detected as a long cut because a requisite for long cut detection is set up circuitwise wherein a long cut is detected only provided that the detector track section continues to be occupied until the first car of the cut arrives in immediate approach of the first of the group of car retarders.

An object of the present invention is to detect long cuts of cars as distinguished from successive spaced short cuts of cars.

Another object of the present invention is to release long cuts of cars in a car retarder at a diierent speed from the speed at which the cars would be automatically released if they were in short cuts.

Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out as the description of the invention progresses.

In describing the invention in detail, reference is made to the accompaying drawings in which parts having similar functions are generally identified in the several figures by similar letter reference characters, and in which:

Figs. 1A and 1B when placed end to end illustrate somewhat schematically one embodiment of a system provided by the present invention for detecting long cuts of cars and governing the release of group `car retarders in accordance with the detection of long cuts;

Figs. 2A-2J (there being no Fig. 21) are track diagrams illustrating different stages in the progress of cuts of cars; and

Figs. 3A-3I (there being no Fig. 3l) are sequence charts illustrating the mode of operation of parts of the system under dierent traic conditions.

For the purpose of simplifying the illustrations and facilitating in the explanation of the invention, various parts and circuits constituting the .embodiment of the invention illustrated have been showndiagrammatically and conventional illustrations have been employed, the drawings having been organized more with the purpose of facilitating an understanding of the principles and mode of operation of the invention than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. The symbols and are employed to indicate connections to the positive and negative terminals of suitable batteries or other sources of direct current. The symbol (B-) is used to indicate connection to the negative terminal of the high voltage power supply used in connection with radar speed responsive apparatus.

With reference to Fig. 1A, the track layout with which one embodiment of the invention is associated is illustrated in part as comprising a stretch of track 10 to which tracks 11 and 12 are connected by track switches STS and ZTS respectively. The right hand ends of the tracks 1i) and 12 are to be considered as forming respective classification tracks wherein freight trains arerespectively made up in a classiiication yard.

According to actual practice, the track layout of a hump classification yard generally includes a relatively large number of classication tracks and track switches governing entrance thereto, and it is to be understood that the present invention is readily applicable to a classication yard of any particular size. The typical section of trackway illustrated in Fig. 1A, however, can be considered typical yof a number of similar sections of trackway that are found in a complete classication yard layout. These larger track layouts generally have as many as eight or ten classification tracks that are fed from each stretch of track including one or more group car retarders such as the car retarders numbers 1 and 2 of Fig. 1A.

Car retarders Nos. l and 2 are disposed end to end respectively in the stretch of track 10 in the approach of the track switch 2TS as a means for providing final retardation for cars proceeding to classification tracks beyond the car retarders to the right.

Although the car retarders numbers 1 and 2 can assume a number of different forms, such as being of either the weight-automatic, or the spring-actuated type, for this embodiment `of the present invention, it is assumed that these car retarders are of the type having spring actuated brake shoes wherein the degree of pressure applied is adjustable by power driven means. A suitable car retarder of this type is disclosed, for example, in the U. S. patent to W. K. Howe, No. 1,852,572, dated April 5, 1932.

Car retarder operating mechanisms as illustrated in block form, are provided for selectively operating the respective car retarders to different degrees of retardation or to release positions as required. These operating mechanisms can be controlled as is disclosed, for example, in the U. S. patent to W. K. Howe, No. 2,038,112 dated April 21, 1936.

For the embodiment of the invention illustrated in Fig. lA, a weighing device WD is used at the entrance end of the car retarder No. 1 for determining the degree of retardation required forcars entering the group car retarders in accordance with the weights of approaching cars. This weighing device need not weigh the entire car, but can be constructed to respond to the weight applied by one wheel of a car as being indicative of the approximate weight that the car is carrying. This Weighing device also serves as a means for rendering `the operation of radar speed responsive apparatus effective to govern the release of the car retarders in `accordance with the speeds of approaching cars.

Near the exit end of each of thecar retarders is a `directional Aantenna DA which is connected 'to suitable kis reduced to respective selected speeds.

radar speed responsive apparatus which is illustrated in Figs. 1A and 1B in block form. This radar speed responsive apparatus is assumed to be of the continuous wave radar type employing the Doppler frequency principle discussed in general terms in chapter 5 of the book entitled Radar System Engineering edited by Louis lVl. Ridenour and constituting volume l of the Radiation Laboratory Series published by the McGraw-Hill Book Company of New York. This radar speed responsive apparatus is sometimes called an interferometen A suitable type of interferometer for this purpose is disclosed, ,for example, in the U. S. application of H. C. Kendall et al., Ser. No. 359,162, led lune 2, 1953. The radar speed responsive apparatus assumed to be employed in the embodiment of the present invention illustrated in Figs. 1A and 1B is assumed to provide improvements over the above mentioned application of H. C. Kendall et al., Ser. No. 359,162 as is disclosed in the U. S. application of H. C. Kendall et al., Ser. No. 513,3 64 led of `even date with the present application.

Associated with each of the car retarders is a pair of weight relays W1 and W2 that are suitably controlled to distinctive conditions in accordance with the weight of an approaching car as may be determined by the weight detector WD. A heavy car is indicated when relay W1 is down and relay W2 is up; a medium weight car is indicated when both relays W1 and W2 are up; and a light Weight car is indicated when relay W1 is up and relay W2 is down.

A speed relay S and an anticipation relay A are provided for each car retarder, these relays being controlled by associated radar speed responsive apparatus so as to be released upon passage of a car when the speed of a car The anticipation relay A is `controlled to release at a slightly higher lspeed than'the speed relay S.

A check relay CK is provided for each of the car retarders for the purpose of rendering effective the automatic control of the associated car retarder in accordance with'the speed of a car, only provided the car is immediately-in approach of the associated car retarder.

An exit relay XR and an associated slow dropping away relay XP is provided for each of the car retarders for the purpose of restoring relays associated with the same car retarderto their normal positions after passage of acar.

AA track relay TR is provided for a conventional detector track section T that is associated vwith the track switch STS. A slow-pick-up back contact repeater relay TP is associatedwith track relay TR.

Track storagestick repeater relays TPS are provided for use in long cut detection, the number of relays TPS required being in accordance with the storage requirements for each particular yard based upon the maximum numberof cuts of cars that would be expected to occupy the portion of trackway illustrated within car retarder No. 1 and in approach thereof. `Each of the storage relays TPS has associated therewith a pair of transfer relays TN and TNP to facilitate the transfer of storages as a car progresses.

A manually operable control lever' RCL is provided for each of the car retarders. This is a control switch having a position for automatic operation and separate positions for the respective degrees of operation of the associated car retarder that may be required for manual operation.

`Having thus described in general the apparatus provided .-in accordance with the present invention, further detail consideration will be given as to the organization of the apparatus and the circuits involved when considering the mode of operation under various typical operating conditions.

Operation A` normal condition that the apparatus assumes when is illustrated in Figs. 1A and 1B wherein all of the relays illustrated are in their deenergized positions except for the track relay TR which is normally energized according to 'usual practice lfor the control of track relays. It is :assumed that normally the levers IRCL and ZROL are in their extreme left-hand positions which renders the control of the car retarders subject to automatic operation.

The car retarders are normally lclosed in accordance with the yassociated check relays CK being in their dropped away positions. This is primarily as a matter of safety to insure that there will always be 'braking available for a car, even though there might lbe a failure in the control apparatus. Thus, for example, energy is normally applied to control wire 4 through normally closed contact 8 of switch lRCL and back contact 9 of the ycheck relay lCK. The closure of this :cincuit insures that the car retarder No. 1 is -operated to its position of maximum retardation under normal conditions. It will be readily apparent that it could as well be normally -operated to positions `of lesser ldegree of retardation in accordance with the requirements of practice.

'When .a car approaches the group car retarders and enters the detector track section T .as is illustrated in IFig. 2A, the detector track relay TR is dropped away, and the dropping away of this relay causes the picking up of the transfer relay ITN. This relay is picked up by the energization of `a circuit extending Ifrom (-1-), including back contact l13 of relay TP, back contact 14 of relay 'TR, back contact 15 `of relay `ITN and lower winding Iof relay 1TN, to The picking up of this relay closes :a stick circuit at `front contact 16 shunting back contact 15 of relay lTNP out `of the circuit -just described. The relay ITN is preferably made slow to drop away by the :shunting of its upper `winding through front contact 17.

The `dropping away of the track relay TR also closes a circuit lfofr the picking up `of yits back contact repeater relay 'DP through 'back contact 18, ibut the relay TP is `suiiiciently slow acting to allow time for the relay ITN to be picked up and also to allow time for the energization of the relay 1TN P.

lIt is to be understood that the setting up of the storage for the "car by the actuation o'f relay ITN may be `accorrrpli-shed by transfer -lfrom la prior storage such as might be provided in automatic switching circuits, rather than in `accordance vwith entrance to lthe track section T as has been `shown land described.

Relay ITNP becomes picked up in response to the picking up vof relay lTN by `the energization of an obvious circuit `for its lower `winding closed at front contact 19 of relay `ITN. This relay when picked up is maintained energized 'by a stick circuit extending 'from through back contacts 20 and 21 of relays ZDNP and ZTN connected in multiple, front contact 22 of relay ITlNP and lower winding of relay ITNP to I(--). Relay `ITNP is preferably made slow to dnop away by the shunting of its upper winding through front contact 23.

Shortly after the relay ITNP has been picked up, the relay TP becomes picked up, thus 'opening the circuit for the energization of relay ITN at back contact 13. Relay ITN then |becomes dropped away.

The fact that the relay ITNP has been picked up registers the presence 'of the car, and this information is stored by the relay lTNP until the information can be transferred to the storage relay ZTNP that is more directly associated with car retarder No. 1. Inasmuch as the relay ZTNP is in its deenergized position under the assumed conditions of traffic, conditions are properly set up for transfer of the storage to the relay ZTNP.

Upon the picking up of relay ITNP, the relay ZTN becomes energized by a circuit extending from (-1-), including front contact 24 of relay lTNP, back contact 25 of relay ZTNP, back contact 26 of relay lXR and lower winding of relay ZTN, to The picking up of this relay establishes a stick circuit at front contact 27 shunting contacts 25 and 26 of relays ZTNP and 1XR respectively out of the circuit that has just been described. Relay ZTN is made slow to drop away by its upper winding being shunted through front contact 28. Although the picking up of relay ZTN opens back contact 21 in the stick circuit for relay ITNP, the relay lTNP is still maintained energized through back contact 20 of relay 2TNP at this time.

The picking up of relay ZTN closes an obvious circuit at front contact 29 for the energization of relay 2TNP, and this relay, when picked up, is maintained energized by a stick circuit having energy applied through back contact 3@ of relay lXP connected in multiple with front contact 31 of relay 1XR and through front contact 32 of relay ZTNP and the lower winding of relay 2TNP. This stick circuit maintains relay 2TNP energized until the car for which the storage is provided leaves the car retarder No. 1 so as to permit the the exit relay 1XR to be dropped away prior to the dropping away of relay 1X1? The picking up of relay ZTNP deenergizes the relay ITNP by the opening of its circuit at back contact 20, and thus relay lTNP is dropped away (it being assumed that the relay 1TN has been dropped away prior to this time). The dropping away of relay ITNP opens the stick circuit at front contact 24 by which the relay 2TN has been maintained picked up and thus causes the dropping away of relay ZTN.

When the car has advanced as is indicated in Fig. 2B so that the track section T has become unoccupied in the rear of the car, the track relay TR is picked up, and its back Contact repeater relay TP is dropped away by the opening of its circuit at back Contact 18.

Upon the picking up of the track relay TR, a circuit is closed for the energization of the track repeater storage relay ZTPS extending from (-l-), including front contact 33 of relay TR, front contact 34 of relay ZTNP, and upper winding of relay ZTPS, to This relay when picked up is maintained energized dependent upon the continued energization of the storage relay ZTNP by a stick circuit extending from including front contact 35 of relay ZTNP, front contact 36 of relay 2TPS and lower winding of relay ZTPS, to

The function that has been performed by the picking up of the relay ZTPS is to condition Retarder No. 1 Speed Modier (indicated in block form in Fig. 1A) so that upon the picking up of the check relay ICK when the car is immediately in approach of car retarder No. 1, the electronic speed modier is effective to determine the speed of release for car retarder No. l in accordance with the performance of the car upon approaching this car retarder. The circuit illustrated in Fig. 1A extending to the block representing Retarder No. l Speed Modier includes back contact 37 of relay 2TPS and front contact 38 of the check relay 1CK in series. The nature of the speed modication in the electronic apparatus is such that it takes place momentarily at the time when the check relay llCK is picked up provided that the modifying means which includes the charge of a condenser (not shown) is not shunted by a circuit including back contact 37 of relay 2TPS in series with the front contact 38 of relay ICK. In other words, if the relay ZTPS is picked up prior to the entrance of a car upon the weight detector WD, the shunt circuit connected to the speed modier is opened by removing the (B-) connection to the shunting circuit through back contact 37 prior to the closure of front contact 38 of the check relay lCK, and in this manner the retarder No. l is permitted to release a car in accordance with performance characteristics that are electronically stored in the Retarder No. l Speed Modier according to a mode of operation fully described in the above mentioned U. S. application of Kendall et al. Ser. No. 513,364 tiled of even date with the present application.

Considering further progress of a car sothat the car enters upon the weight detector WD as is illustrated in 6 the track diagram of Fig. 2C, the check relay ICK is picked up, and upon the picking up of this relay, modification in the control of the speed relay 1S and the anticipation relay 1A is rendered eiective so as to render these relays subject to release at respective car speeds selected in accordance with the performance of the car in approaching car retarder No. 1 as to its degree of rolling resistance.

At the time when the check-relay lCK is picked up, the control of car retarder No. 1 operating mechanism is rendered operative in accordance with the speed and weight of the approaching car. For most cars, the relays 1S and 1A are already in their picked up positions because of the speed of the respective approaching cars being such as to require retardation, and the weight storage relays IlWll and 1W2 are positioned in accordance with the car weight as registered by the weight detector WD, or any other suitable means.

If it is a heavy weight car that is approaching car retarder No. 1 relay 1W 1 is in its dropped away position and relay 1W2 is in its picked up position. Thus, the retarder operating mechanism is provided with energy applied to wire No. 4 to maintain maximum retardation. Energy is applied to wire No. 4 under these conditions through contact 8 of the manual control switch IRCL, front contact 9 of relay llCK, front contact 40 of relay 1S, back contact 41 of relay IWI, front contact 42 of relay 1W2, and front Contact 43 of relay 1A.

lf it is a medium weight car that is approaching car retarder No. 1, the car retarder is operated toits No. 3 position for applying a lesser amount of retardation in accordance with the application of energy to wire No. 3 through contact 8 of switch IRCL, front contact 9 of relay lCK, front contact 40 of relay 1S, front contact 41 of relay 1W1, front contact 44 of relay 1W2, and front Contact 45 of relay 1A.

If it is a light weight car that is approaching car retarder No. l, still lesser retardation is provided because of application of energy to control wire No. 2 through contact S of switch lRCL, front contact 9 of relay 1CK, front contact 4@ of relay 1S, front contact 4-1 of relay 1W1, back Contact 44 of relay 1W2, and front Contact 46 of relay 1A.

As the speed of the car is reduced, the anticipation relay 1A becomes dropped away before the dropping away of relay 1S, and the shifting of the contacts 4S, 46 and 43 of relay 1A to open their front contacts and 'close their back contacts provides that the operating mechanism of the car retarder No. 1 is operated to its next position of lesser retardation. When the speed of the car is linally reduced to the speed which has been predetermined as being proper for the release of the car from retardation, the relay 1S becomes dropped away, and the: dropping away of this relay provides for the opening of the car retarder by the application of energy to wire No. 0 through contact S of the switch IRCL, front contact 9 of relay lCK, and back contact 40 of relay 1S. The car retarder when thus opened is maintained opened unt-il the dropping away of the check relay 1CK after the car has left the car retarder No. l as will be more readily apparent as the description progresses. When relay lCK becomes dropped away, the circuit described for the application of energy to wire No. 0 is opened at front contact 9 of relay CK, and the `closure of back contact 9 establishes a circuit that has been described as being normally closed for application of energy to wire No. 4 to restore car retarder No, 1 to its closed position.

As the car proceeds in the track layout to the position indicated in Fig. 2D so that it is substantially close to the exit end of car retarder No. l, the intensity of the reected signal from the car in the radar speed responsive apparatus has become so great as to ettect the picking up of the relay IXR as is indicated in the sequence chart of Fig. 3D. The picking up of relay lXR causes the picking up of its repeater relay 1XP by the energiza tion of an obvious circuit closed at front contact 39 of relay lXR. Relay 1XP is made slow in dropping away by the shunting of its upper Winding through front contact 53 for the purpose of providing a clear-out interval upon the dropping away of the relay lXR after the car has left car retarder No. 1.

When the car has progressed as illustrated in Fig. 2E to the point of having left the car retarder No. l entirely, the relay 1XR becomes dropped away, and upon the dropping away of that relay, with the relay lXP held up by its slow action, energy is removed from the stick circuit that has been described for the relay ZTNP so as to cause that relay to be dropped away. Relay ZTNP when dropped away causes the dropping away of relay ZTPS by the opening of its stick circuit at front contact 35 and pick-up circuit at front contact 34. The control of the relay 1CK is such that this relay is dropped away by the dropping away of relay lXR or the loss of signal strength, and thus the condition of the relays associated with the control of car retarder No. l have been restored to their normal conditions.

A similar mode of operation to that which has been described for the control of car retarder No. l is provided for the passage of the car through retarder No. 2. The check relay ZCK is picked up as is disclosed in the above mentioned Kendall et al. application Ser. No. 513,364 filed of even date with the present application upon the pick-ing up of the exit relay lXR when the car approaches the entrance end of car retarder No. 2. It will be readily recognized that the degree of retardation is selected in the same manner as has been described for car retarder No. 1 by similar circuits which are shown in Fig. 1B, the car retarder No. 2 being opened when the speed of the car has been reduced to a predetermined value so as to cause the dropping away of relay 2S to apply energy to the wire No. for the power operation of the car retarder operating mechanism for car retarder No. 2 to its open position. lt will be noted that the car speed at which the speed relay 2S is released is substantially the same as the car speed at which relay 1S is released because the control of relay 2S is by Retarder No. 2 Speed Modifier which is so governed as to provide the same release speed for the relay 2S as the release speed for the relay 1S that is provided by Retarder No. l Speed Modier. This type of control is provided because of electronic storage and transfer means by which the condition of modification set up in Retarder No. l Speed Modifier is transferred as is illustrated by the line 47 to Retarder No. 2 Speed Modifier.

Having thus described the mode of operation upon passage of a single car, consideration will now be given as to the mode of operation wherein a second car enters the detector track section T before a first car has passed through car retarder No. l. Thus the entrance of a second car into the track section T can be considered as taking place under conditions of progress of the first car as illustrated in either Fig. 3C or 3D. The conditions of storage of the presence of the first car will be assumed to have been set up according to a mode of operation as has been heretofore described.

The entrance of the second car into the track section T causes the picking up of the transfer relay lTN by the energization of a circuit that has been described, and upon the picking up of this relay, the repeater relay 1TNP is picked up, and the relay lTN becomes released upon the picking up of relay TP by the opening of back contact 13. Because of the relay ZTNP being in its energized position at this time on account of the presence of the first car, back contact 25 of relay 2TH? in the pick-up circuit for the relay ZTN is open, and thus the relay ZTN cannot be picked up at this time in accordance with the picking up of relay lTNP. Thus the relay ITNP becomes effective to store the indication of the presence of the second car, and this storage is maintained until the first car has passed out of the car retarder No. l so as to permit the dropping away of the exit relay lXR prior to the dropping away of its slow repeater relay 1XP. Under these exit conditions the dropping away of relay ZTNP closes back contact and permits the picking up of relay ZTN and the subsequent transfer of the storage for the second car so as to pick up the relay ZTNP and eventually cause the dropping away of the relay lTNP. The mode of operation upon progress of the second car beyond this assumed condition is substantially the same as that which has been described in detail with reference to the passage of a first car, the relay ZTPS being picked up when the track section T becomes unoccupied in the rear of the second car so as to open back contact 37 prior to the picking up of relay 1CK to close front contact 38 so that there is no shunt applied on the Retarder No. l Speed Modifier, thus permitting speed modification to be effective in a manner which has been described.

If the second car were to leave the track section T prior to the first `car having left car retarder No. l, the relay lTPS would be picked up through front contact 33 of relay TR and front .contact 48 -of relay ITNP. This relay when picked up is maintained energized by a stick circuit including front contact 49 of relays ITPS and front contact 48 of relay ITNP. The picking up of relay lTPS is accomplished to store the information that the second car is a short cut and thus should have automatic retarder control according to its performance in approaching the car retarder, as compared to the system of control for the car retarder that will be hereinafter described as being effective upon the passage lof long cuts of cars. When the first car has passed out of the car retarder No. l so as to permit transfer of the storage of the presence of the second car into the relay ZTNP, the picked up condition of relay 1TPS is also transferred by the picking up of relay ZTPS by a circuit -including front contact 50 of relay lTPS and f-ront contact 51 of relay ZTN. It will be readily apparent that upon the dropping away of relay ITNP after transfer has been completed, the opening of front contact 48 causes the `dropping away of relay ITPS.

The mode of operation upon the passage of a long cut of cars is substantially the same as has been described eX- cept that the track section T never becomes unoccupied prior to the entrance of the cut into the car retarder No. 1 and thus there -is no opportunity for picking up the relay ZTPS or the relay ITPS. With relay Z'I'PS in its dropped away position at the time when the head end of the cut actuates the weight ydetector WD, the check relay 1CK is picked up and thus a shunt is applied from (B-) through back contact 37 of relay ZTPS and front contact 38 of relay 1CK to the Retarder No. l Speed Modifier which renders the speed modifier ineffective and thereby causes the speed relay 1S to be maintained picked up until the speed of the cut has been reduced to a speed substantially below the speed at which a single car would normally be released. Because of Retarde-r No. l Speed Modifier being shunted at the time of entrance of the cut into car retarder No. l, there is no modification storage set up in the Retarder No. l Speed Modifier to be transferred over wire 47 t-o Retarder No. `2 Speed Modifier, and thus the speed relay 2S of retarder No. 2 will be released at the same low speed as is provided for the cut by the car retarder No. l in accord-ance with the dropping away of the speed relay 1S.

Although the track relay TR becomes picked up when the Irear end of the cut passes out of the track section T, and the relay ZTPS becomes picked up to open back contact 37, this can have no bearing upon the Car Retarder No. l Speed Modifier because this modifier is subject to control only at the time when the check Irelay 1CK is initially picked up upon the first actuation of the weight detector WD. Thus the low release speed for the speed relays 1S and 2S as selected by the modifier having been initially shunted is maintained effective until the cut of cars passes entirely out of the associated car retarders.

Having described one specific embodiment of the present invention as a typical form which the invention may assume, it is to be understood that this form is selected principally to facilitate the disclosure of the invention, rather than to limit the number of forms the inventio-n may assume, and it is Ito be further understood that various adaptations, modifications, and alterations may be made to the specific `form shown in accordance with the requirements of practice except as limited by the appending claims.

What I claim is:

1. In a car retarder control system, a stretch of railway track including a car retarder `and a track section spaced a predetermined distance in approach of the car retarder, speed responsive apparatus for automatically governing the release of said car retarder when a car within the car retarder has reduced its speed to a selected release speed, speed modification means for selecting the release speed of said speed responsive means, and means for rendering said modification means ineffective when the first car of a cut is about to enter the car retarder only provided that said track section has been continuously occupied upon passage of the cut of cars until said iirst car of the cut has progressed to a point immediately in approach of the car retarder.

2. In ya car retarder control system, a stretch of railway track including a car retarder and a Itrack section spaced a predetermined distance in approach of the car retarder, speed responsive apparatus effective when initiated to automatically release the car retarder when a car has reduced its speed to a selected release speed, a device subject to actuation by a car immediately in approach of the car retarder, initiating means including lsaid device for rendering said speed responsive apparatus effective, circuit means for selecting the release speed of said speed responsive apparatus, and means acting upon said circuit means to select a given distinctive predetermined speed of release only provided that said track section is continuously occupied upon passage of a cut of cars until the first car of the cut as progressed to a point wherein said device is actuated.

3. In a car retarder control system, a stretch of railway track including a car retarder and a track section spaced a predetermined dist-ance in advance of the car retarder, radar speed responsive apparatus for automatically governing the release of said car retarder when a car within the car retarder has reduced its speed to a selected release speed, said radar speed responsive apparatus having a directional antenna with `a radiation pattern including the area of the trackway in which the car retarder is located, speed modification means for selecting the release speed of said radar speed responsive means, and means for rendering said speed modification means inelective when a car is about to enter the car retarder only provided that said track section is continuously occupied upon passage of a cut of `oars until the first car of the cut has progressed to a point immediately in approach of said car retarder and within the radiation pattern of said antenna.

4. In a car retarder control system, la stretch of railway track including la car retarder and a track switch spaced a predetermined distance in advance of the car retarder, a detector track section for said track switch, speed responsive apparatus for automatically governing the release of `said car retarder when a car within the car retarder has reduced its speed to a selected release speed, speed modification means for selecting the release speed of said speed responsive means, and means for 4rendering said speed modication means ineffective when a car is about to enter the car retarder provided that said detector track section has been continuously occupied until the first car of a cut of cars has progressed to a point immediately in approach of the car retarder.

5. In a car retarder control system, `a `stretch of railway track including a car retarder and a track section spaced a predetermined distance in approach of the car retarder, speed responsive apparatus for automatically governing the opening of said car retarder when a car within the car retarder has reduced its speed to a selected release speed, speed modification means for selecting the release speed of said speed responsive apparatus, a track repeater relay, circuit means for energizing said track repeater relay when said track section is unoccupied, said circuit means being rendered effective only provided there is a car between said track section and the exit end of said car retarder, and means for rendering `said modification means inetfective when a car is about to enter the car retarder except when said track repeater relay is energized.

6. In a car retarder control system, a stretch of railway track including a car retarder and a track section spaced a predetermined distance in approach of the car retarder, speed responsive apparatus for -automatically governing the opening of said car retarder when a car within the car retarder has reduced its speed to a selected release speed, speed modification means for selecting the release speed of said speed responsive apparatus, a track repeater relay, circuit means for energizing said track repeater relay when said track section is unoccupied, said circuit means being rendered eiective only provided there is a car between said track section and the exit end of the car retarder, and means selected by said track repeater relay for selectively rendering said modification means effective or ineffective in accordance with whether a short or a long cut of cars is approaching said car retarder.

7. In a car retarder control system, a stretch of railway track including a car retarder and a track section spaced a predetermined distance in approach of the car retarder, speed responsive apparatus for automatically governing the opening of said car retarder when a car Within the car retarder has reduced its speed to a selected release speed, speed modification means for selecting the release speed of said speed responsive apparatus in accordance with the performance of a car in approaching the car retarder, a track repeater stick relay, pickup circuit means for energizing said track repeater stick relay when said track section is unoccupied provided that there is a car between said track section and the exit end of the car retarder, stick circuit means for maintaining said track repeater stick relay energized until a car has left the car retarder, and means selected by said track repeater stick relay for selectively rendering said modification means effective or ineffective in accordance with whether a short or a long cut of cars is approaching said car retarder.

References Cited in the le of this patent UNITED STATES PATENTS 2,629,865 Barker Feb. 24, 1953 

